Operator presence sensor for operator&#39;s seat

ABSTRACT

An operator presence sensor for an operator&#39;s seat on equipment, such as skid steer loaders and the like, provides a signal to indicate when the seat is occupied. The operator presence is sensed by permitting seat rails to pivot about their forward end against leaf springs designed to support the seat weight plus a known fraction of an operator&#39;s weight so that the rear of the seat is raised when the seat is unoccupied and when an operator occupies the seat the springs deflect and the rear of the seat moves down, resting on a seat support pan. An electronic sensor detects seat position to provide a position signal.

BACKGROUND OF THE INVENTION

The present invention relates to an operator presence sensing systemthat permits a seat to be mounted on adjustable seat rails for ease ofpositioning in fore and aft direction, while providing a signalindicating when the seat is supporting more than a desired amount ofweight.

Vehicle seat switches have been used in the past for determining thepresence of an operator, so that various interlocks can be actuated whenthe operator is not present on the seat. Improved reliability of thesesystems is sought, particularly when the vehicle is used where dirt andother foreign objects are present.

It is further desirable to have the seat adjustable in the same mannerthat they presently are adjustable, while maintaining the reliability ofthe sensing system.

U.S. Pat. No. 5,124,512 shows a vehicle seat switch which utilizes abase panel that moves up and down and actuates a spring loadedmechanical switch at the forward edge of the unit. A wire type spring orspring frame is utilized and a base plate acts against the spring framesto cause actuation of an existing switch, such as a microswitch. In asecond form of the invention a switch actuator comprising a bowed leafspring that is straightened under load actuates a mechanical switch.

Adjusting the seat utilizing this type of arrangement is not disclosedin the patent, and it appears that making the seat adjustable involvesadditional structural components, and would complicate the overalloperation of the seat.

U.S. Pat. No. 4,075,443 illustrates a type of switching mechanism thatoperates on the springs within a seat cushion. This permits the seat tobe mounted in normal manner on adjustable rails that permit sliding ofthe seat, but the positioning of a switch for accurate operation inrelation to the seat springs is difficult to precisely maintain, and itappears from the construction that adjustment would be difficult.

A sensing apparatus that has switches along the lateral side of the seatis shown in U.S. Pat. No. 4,361,741. The operation relies upon apivoting plate in one form of the invention, and in another form of theinvention depends on deflection of the seat spring itself for actuation.A feature of this patent is to control the force that is applied to themechanical switch to avoid damage to the switch itself.

SUMMARY OF THE INVENTION

The present invention relates to an operator presence sensor that issensitive to the presence of an operator in a vehicle seat, and providesa signal indicating if the seat is occupied. The signal is used forfurther controls such as locking in or locking out of the hydrauliccircuits on a skid steer loader. A pivoting seat is provided which has apivot system that includes a leaf spring below one or both of the twoadjustable seat rails and above a seat pan that is used for supportingthe seat. The forward edge of each seat rail is clamped to the seat panpermitting no relative movement between the rail and the seat pan. Thiscauses the inclusion of the seat pan into the spring system because ofthe seat pan and spring deflection that occurs when the operatoroccupies the seat.

The leaf springs used are directly below the rails, and will support theseat plus a predetermined amount of weight under a spring load, so thatthe rear of the seat is suspended above the seat pan when the seat isunoccupied. When the operator occupies this seat, the springs deflectand the rear of the seat moves down until the rails rest on the seatpan, and this movement, as shown, is sensed by a Hall effect sensor.

The use of the springs directly under the seat rails permits the seat tobe adjusted in a normal manner along the rails, and yet a directpivoting action of the seat between occupied and unoccupied positions isprovider. There can be two leaf springs used, one under each seat rail,or only one leaf spring then preferrably under the rail that isconnected to the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an operator presence sensing systemmade according to the present invention;

FIG. 2 is a rear elevational view of the seat system of 1;

FIG. 3 is an enlarged partial sectional view showing a seat railattachment used with the system in FIG. 1;

FIG. 4 is an enlarged sectional view of the sensor assembly used in theoperator presence sensing system of the present invention; and

FIG. 5 is a sectional view taken as in line 5--5 in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An operator seat indicated 10 which can be for an off road vehicle, suchas a skid steer loader, is supported relative to the vehicle frame (notshown) through the use of a seat pan 12 which has a substantiallyhorizontal bottom wall 14, and which is formed with vertical side walls16 that are formed upwardly to provide reinforcement and mounting. Asshown in FIG. 2 schematically, the side walls 16 can have a horizontalattachment flange at the upper edges. The seat pan is supported on avehicle frame in a suitable manner.

Normally, the seat includes a seat cushion assembly 18, and a back 20,which may be hinged together about a suitable hinge member indicated at22. The seat cushion assembly 18 generally includes a lower support wall24 that is formed to provide attachment regions as shown in FIG. 1comprising bosses 26 at the front, and bosses 28 at the rear. A separateseat rail assembly 30 is then bolted to the seat cushion support wall 24at each of the bosses 26 and 28 adjacent lateral edges of the seat in anormal manner. The seat rail assemblies 30 permit adjustment of the seatin longitudinal direction. As schematically shown in FIG. 2, the seatrail assemblies include a base rail 32, and a longitudinally slidingupper rail 34. The sliding upper rail 34 of each rail assembly isfastened to the seat support plate 24 at bosses 26 and 28. The upper andlower rails on one rail assembly 30 can be retained from slidingrelative to each other by a conventional latch, and by releasing aschematically shown latch lever 36 the two rails of the respective railassembly on each side of the seat can be slid longitudinally relative toeach other on ball bearings. The seat adjustment is used for positioningof the seat in fore and aft direction.

The forward end of the base rail 32 is mounted directly to the seat pan12 in a relatively flexible, flat portion of wall 14 the pan. The seatwall pan 14 itself is somewhat flexible or springy at the rail frontattachment location. A securing member for the seat rail assemblies 30comprises a threaded stud 38 that is pressed into the base rail 32 andpasses through a first spacer washer 39, and then through the seat pan14. The spacer washer 39 is used for providing a space between the lowersurface of the front end of the base rail 32 and the top of the seat pan14 to provide clearance for a leaf spring 40 that has an openingslightly larger than the spacer washer 39 and receives the washer so theleaf spring can move slightly.

A second washer 42 is used on the lower side of the seat pan wall 14,and a suitable nut 43 is used for tightening the stud 38 down andholding the front end of the base seat rail securely relative to theseat pan 14. The mounting of the base rail 32 is the same on both sidesof the seat, and there is a spring 40 on one or both sides of the seatas well.

Spring 40 has a bend adjacent the front end as at 44, so that it restsagainst the bottom of the base rail 32 and then tapers down toward thetop of the seat pan wall 14. In turn the leaf spring has a bend portion45 approximately a third to one half of the distance toward the rear endof the seat rail assembly, as shown in FIG. 1. The rear of the leafspring 40 thus extends upwardly so that its rear portion rests againstthe bottom of the base rail 32 and provides a biasing force tending tolift the rear of the seat rail assembly. Thus the entire seat assemblyis moved upwardly away from the seat pan wall 14. Both of the seat railassemblies 30 on the opposite sides of the seat are supported in thesame manner, when two leaf springs are used.

A bushing 46 is mounted onto a stud 48 attached to the rear end of oneof the base rails 32 and is held in place on the stud. The bushing 46fits into a "U" shaped end slot of the spring 40 to hold the spring inplace. A sensor support housing wall 50 is bolted to the bottom surfaceof the seat pan 14 in alignment with the one seat rail carrying thebushing. The bushing 46 passes down through an opening in the seat panand through an opening in a flange 52 on housing 50. A magnet carriercollar 53 is mounted on the bushing 46 below the flange 52 and as can beseen the collar 53 is larger diameter than the opening in flange 52 sothat the collar acts as an upward stop for the seat rail on which it isattached.

It can thus be seen that in normal operation with no operator on theseat, the rail assemblies 30 will be pushed up away from the seat pan,but with greater than a predetermined weight, for example 30 pounds, onthe top of the operator's seat, the rear of the seat rail assemblieswill pivot downwardly about the fastening of the front ends of the railassemblies to the seat pan. In effect, the seat pan wall 14 enters intothe overall spring system, but permits pivoting seat rail movement asthe pan wall 14 deflects when the rear of the seat rail assemblies movedownwardly. In place of the seat rail fastening pivot shown, a bearingor other conventional pivot construction can be provided.

The housing 50 includes a portion adjacent the magnet carrier collar 53.A Hall effect sensor 56 is mounted in the housing 50 and is positionedin alignment with a first magnet 60 on the magnet carrier collar withthe seat unoccupied as shown in FIG. 4. When the predetermined weight isapplied the rear of the seat the rails moves downwardly and the magnetcarrier collar 53 also moves downwardly to a position where a secondmagnet 61 is aligned with the Hall effect sensor 56.

Magnet 60 has a magnetic north pole facing the sensor 56 and magnet 61has a magnetic south pole facing the Hall effect sensor 56. The Halleffect sensor 56 is sensitive to the polarity of the magnets. Thus, whenthe magnet 60 is adjacent to Hall effect sensor 56 there is a positiveindication that the seat is unoccupied, and when the magnet 61 isaligned with or moves past the Hall effect sensor 56 as the seat movesdownwardly, there is a second positive signal that the seat is occupiedis received. This provides two positioning signals, which are used forthe overall system operation. The magnetic poles facing the Hall effectsensor can be reversed in position if desired. The collar 53 is heldproperly oriented relative to the Hall effect sensor by a suitablesliding key. As shown a finger like key 70 that slides in a bore 71formed in the magnet carrier collar 53 as the seat and thus the collar53 move up or down. The finger like key 70 is fixed to the flange 52 andslipped into place in the bore 71 when the collar is installed on thebushing 46.

The positive sensing of the operator presence or absence, provides asignal that indicates that an operator is or is not in the seat. Thesensing system utilizing a Hall effect sensor and a magnet that affectsthe output of the Hall effect sensor is not affected by rust or dirt orforeign materials, and there is no contact between the components.

The seat rail assembly 30 on the other side of the seat pan does nothave a sensor, but the stud 48 on the rear of that rail has a sleeve 67thereon that passes through an opening in the seat pan wall 14. A washer63 and lock nut 64 are placed below the seat pan and hold the sleeve 67in place. The washer 63 provides an upward stop for the seat at thedesired level. This means both seat rails are stopped in upwarddirection and the leaf spring is used to preload the rails upwardlyagainst the stops. The sleeve 67 also fits into a "U" shaped slot at therear end of the aligning spring 40 to keep it in place below the baserail 32.

Again, as stated where the seat is relatively light weight only one leafspring under one rail will work satisfactorily.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. An operator presence sensor for the seat of avehicle comprising a base plate, a longitudinal rail member supportingthe seat, a forward end of the rail member mounted relative to the baseplate to permit movement of a rear end of the rail member, a leaf springmounted relative the base plate and proximate the forward end, the leafspring extending along substantially the entire length of thelongitudinal rail member and having a portion that is bent to beardirectly on the rail member and deflect the rear end of the rail memberand the seat upwardly, the rear end of the rail member being movabletoward and away from the base plate, a position sensor having twocomponents, one mounted relative to the rail member and the othercomponent being mounted relative to the base member to sense movement ofthe rear end of the rail member when a predetermined load is placed onthe seat and the leaf spring deflects a predetermined amount.
 2. Thepresence sensor of claim 1 and a bushing fixed to the rear end of therail member and extending through an opening in the base plate to alower side of the base plate, the one component of the position sensorbeing mounted on said bushing below the base plate.
 3. The presencesensor of claim 2 wherein the other component comprises a Hall effectsensor for sensing presence of a magnetic field from a magnet mounted onthe bushing.
 4. The presence sensor of claim 3 wherein said magnetcomprises at least two magnetic poles positioned to affect the Halleffect sensor to indicate two positions of the seat.
 5. The presencesensor of claim 3 wherein the seat is supported on a pair of laterallyspaced rail members and each rail member is mounted to permit the rearend thereof to move relative to the base plate, and wherein each railmember has a leaf spring associated therewith.
 6. The presence sensor ofclaim 1 and means to fix the front end of the rail member to the baseplate comprising a stud that is fixed to the rail member, and a spacerbetween the rail and the base plate, the leaf spring having an openingtherein receiving the spacer so the leaf spring is held between the railmember and the base plate when the rail member is clamped by the stud tothe base plate.
 7. An operator's presence sensor for the seat of avehicle having a base plate and a seat supported on adjustable railsrelative to the base plate, the improvement comprising forward ends ofthe rails being mounted relative to the base plate for permitting rearends of the rails to move up and down relative to the base plate, a leafspring extending substantially the entire length along at least onelongitudinal rail and having a portion that is bent to resilientlydeflect rearward portions of the rails upwardly wherein the leaf springis connected to the base plate and the forward end of the at least onerail, a sensor component mounted on the rear portion of one rail andmovable with the rail as the rails move toward and away from the baseplate, and a second sensor component spaced-apart from the sensorcomponent and mounted to sense movement of the one component when theleaf spring deflects a predetermined amount wherein the sensorcomponents remain spaced-apart from each other as the rails move up anddown relative the base plate.
 8. The presence sensor of claim 7 whereinsaid leaf spring has a bend in the midportion thereof such that rear endof the leaf spring contacts the associated rail to urge the seat awayfrom the base plate.
 9. The presence sensor of claim 8 wherein there aretwo leaf springs, one associated with each rail.
 10. The presence sensorof claim 9 and means connected to each rail to limit the movement of therear ends of the rails in a direction away from the base plate.